Methods
C
Instance Public methods
cache(name = {}, options = nil, &block)

This helper exposes a method for caching fragments of a view rather than an entire action or page. This technique is useful caching pieces like menus, lists of newstopics, static HTML fragments, and so on. This method takes a block that contains the content you wish to cache.

See ActionController::Caching::Fragments for usage instructions.

Examples

If you want to cache a navigation menu, you can do following:

<% cache do %>
  <%= render :partial => "menu" %>
<% end %>

You can also cache static content:

<% cache do %>
   <p>Hello users!  Welcome to our website!</p>
<% end %>

Static content with embedded ruby content can be cached as well:

<% cache do %>
  Topics:
  <%= render :partial => "topics", :collection => @topic_list %>
  <i>Topics listed alphabetically</i>
<% end %>

Source: show | on GitHub 

# File actionpack/lib/action_view/helpers/cache_helper.rb, line 34
def cache(name = {}, options = nil, &block)
  if controller.perform_caching
    safe_concat(fragment_for(name, options, &block))
  else
    yield
  end

  nil
end